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Date: Sat, 08 Jun 2013 12:56:00 +0300
From: Stratos Karafotis <stratosk@...aphore.gr>
To: "Rafael J. Wysocki" <rjw@...k.pl>, Borislav Petkov <bp@...e.de>
CC: Viresh Kumar <viresh.kumar@...aro.org>,
Thomas Gleixner <tglx@...utronix.de>,
Ingo Molnar <mingo@...hat.com>,
"H. Peter Anvin" <hpa@...or.com>, linux-pm@...r.kernel.org,
cpufreq@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 1/3] cpufreq: ondemand: Change the calculation of target
frequency
On 06/07/2013 11:57 PM, Rafael J. Wysocki wrote:
> On Friday, June 07, 2013 10:14:34 PM Stratos Karafotis wrote:
>> On 06/05/2013 11:35 PM, Rafael J. Wysocki wrote:
>>> On Wednesday, June 05, 2013 08:13:26 PM Stratos Karafotis wrote:
>>>> Hi Borislav,
>>>>
>>>> On 06/05/2013 07:17 PM, Borislav Petkov wrote:
>>>>> On Wed, Jun 05, 2013 at 07:01:25PM +0300, Stratos Karafotis wrote:
>>>>>> Ondemand calculates load in terms of frequency and increases it only
>>>>>> if the load_freq is greater than up_threshold multiplied by current
>>>>>> or average frequency. This seems to produce oscillations of frequency
>>>>>> between min and max because, for example, a relatively small load can
>>>>>> easily saturate minimum frequency and lead the CPU to max. Then, the
>>>>>> CPU will decrease back to min due to a small load_freq.
>>>>>
>>>>> Right, and I think this is how we want it, no?
>>>>>
>>>>> The thing is, the faster you finish your work, the faster you can become
>>>>> idle and save power.
>>>>
>>>> This is exactly the goal of this patch. To use more efficiently middle
>>>> frequencies to finish faster the work.
>>>>
>>>>> If you switch frequencies in a staircase-like manner, you're going to
>>>>> take longer to finish, in certain cases, and burn more power while doing
>>>>> so.
>>>>
>>>> This is not true with this patch. It switches to middle frequencies
>>>> when the load < up_threshold.
>>>> Now, ondemand does not increase freq. CPU runs in lowest freq till the
>>>> load is greater than up_threshold.
>>>>
>>>>> Btw, racing to idle is also a good example for why you want boosting:
>>>>> you want to go max out the core but stay within power limits so that you
>>>>> can finish sooner.
>>>>>
>>>>>> This patch changes the calculation method of load and target frequency
>>>>>> considering 2 points:
>>>>>> - Load computation should be independent from current or average
>>>>>> measured frequency. For example an absolute load 80% at 100MHz is not
>>>>>> necessarily equivalent to 8% at 1000MHz in the next sampling interval.
>>>>>> - Target frequency should be increased to any value of frequency table
>>>>>> proportional to absolute load, instead to only the max. Thus:
>>>>>>
>>>>>> Target frequency = C * load
>>>>>>
>>>>>> where C = policy->cpuinfo.max_freq / 100
>>>>>>
>>>>>> Tested on Intel i7-3770 CPU @ 3.40GHz and on Quad core 1500MHz Krait.
>>>>>> Phoronix benchmark of Linux Kernel Compilation 3.1 test shows an
>>>>>> increase ~1.5% in performance. cpufreq_stats (time_in_state) shows
>>>>>> that middle frequencies are used more, with this patch. Highest
>>>>>> and lowest frequencies were used less by ~9%
>>>
>>> Can you also use powertop to measure the percentage of time spent in idle
>>> states for the same workload with and without your patchset? Also, it would
>>> be good to measure the total energy consumption somehow ...
>>>
>>> Thanks,
>>> Rafael
>>
>> Hi Rafael,
>>
>> I repeated the tests extracting also powertop results.
>> Measurement steps with and without this patch:
>> 1) Reboot system
>> 2) Running twice Phoronix benchmark of Linux Kernel Compilation 3.1 test
>> without taking measurement
>> 3) Wait few minutes
>> 4) Run Phoronix and powertop for 100secs and take measurement.
>
> Well, while this is not conclusive, it definitely looks very promising. :-)
>
> We're seeing measurable performance improvement with the patchset applied *and*
> more time spent in idle states both at the same time. I'd be very surprised if
> the energy consumption measuremets did not confirm that the patchset allowed
> us to reduce it.
>
> If my computations are correct (somebody please check), the cores spent about
> 20% more time in idle on the average with the patchset applied and in addition
> to that the cc6 residency was greater by about 2% on the average with respect
> to the kernel without the patchset.
>
> We need to verify if there are gains (or at least no regressions) with other
> workloads, but since this *also* reduces code complexity quite a bit, I'm
> seriously considering taking it.
>
>> I will try to repeat the test and take measurements with turbostat as
>> Borislav suggested.
>
> Please do!
>
> Thanks,
> Rafael
>
Hi,
I repeated the tests extracting results from turbostat.
Measurement steps with and without this patch:
1) Reboot system
2) Running twice Phoronix benchmark of Linux Kernel Compilation 3.1 test
without taking measurement
3) Wait few minutes
4) Run Phoronix and turbostat (-i 100) and take measurement
Thanks,
Stratos
------------------------------------------------------------------
Test WITHOUT this patch:
Phoronix Test Suite v4.6.0
Installed: pts/build-linux-kernel-1.3.0
System Information
Hardware:
Processor: Intel Core i7-3770 @ 3.40GHz (8 Cores), Motherboard: ASUS CM6870, Chipset: Intel Xeon E3-1200 v2/3rd, Memory: 2 x 4096 MB DDR3-1600MHz HY64C1C1624ZY, Disk: 1000GB Seagate ST1000DM003-9YN1, Graphics: NVIDIA GeForce GT 640 3072MB, Audio: Realtek ALC892, Monitor: S23B350, Network: Realtek RTL8111/8168 + Ralink RT3090 Wireless 802.11n 1T/1R
Software:
OS: Fedora 18, Kernel: 3.10.0-rc3v+ (x86_64), Desktop: KDE 4.10.3, Display Server: X Server 1.13.3, Display Driver: nouveau 1.0.7, File-System: ext4, Screen Resolution: 1920x1080
Would you like to save these test results (Y/n): n
Timed Linux Kernel Compilation 3.1:
pts/build-linux-kernel-1.3.0
Test 1 of 1
Estimated Trial Run Count: 3
Estimated Time To Completion: 2 Minutes
Running Pre-Test Script @ 12:38:35
Started Run 1 @ 12:38:46
Running Interim Test Script @ 12:38:59
Started Run 2 @ 12:39:03
Running Interim Test Script @ 12:39:14
Started Run 3 @ 12:39:18
Running Interim Test Script @ 12:39:27 [Std. Dev: 8.57%]
Started Run 4 @ 12:39:31
Running Interim Test Script @ 12:39:41 [Std. Dev: 8.56%]
Started Run 5 @ 12:39:44
Running Interim Test Script @ 12:39:54 [Std. Dev: 8.05%]
Started Run 6 @ 12:39:58 [Std. Dev: 7.57%]
Running Post-Test Script @ 12:40:07
Test Results:
10.280334949493
11.148964166641
9.3881862163544
9.3307340145111
9.3948450088501
9.3976459503174
Average: 9.82 Seconds
cor CPU %c0 GHz TSC SMI %c1 %c3 %c6 %c7 CTMP PTMP %pc2 %pc3 %pc6 %pc7 Pkg_W Cor_W GFX_W
38.86 3.57 3.39 0 10.07 2.98 48.09 0.00 44 44 0.00 0.00 0.00 0.00 26.23 20.28 0.00
0 0 33.32 3.65 3.39 0 19.88 3.26 43.54 0.00 44 44 0.00 0.00 0.00 0.00 26.23 20.28 0.00
0 4 48.87 3.52 3.39 0 4.32
1 1 35.58 3.67 3.39 0 12.93 3.28 48.21 0.00 39
1 5 42.12 3.51 3.39 0 6.39
2 2 33.42 3.66 3.39 0 13.11 2.78 50.69 0.00 34
2 6 40.83 3.43 3.39 0 5.70
3 3 35.97 3.68 3.39 0 11.51 2.61 49.92 0.00 39
3 7 40.75 3.49 3.39 0 6.73
---------------------------------------------------------------------
Test WITH this patch:
Phoronix Test Suite v4.6.0
Installed: pts/build-linux-kernel-1.3.0
System Information
Hardware:
Processor: Intel Core i7-3770 @ 3.40GHz (8 Cores), Motherboard: ASUS CM6870, Chipset: Intel Xeon E3-1200 v2/3rd, Memory: 2 x 4096 MB DDR3-1600MHz HY64C1C1624ZY, Disk: 1000GB Seagate ST1000DM003-9YN1, Graphics: NVIDIA GeForce GT 640 3072MB, Audio: Realtek ALC892, Monitor: S23B350, Network: Realtek RTL8111/8168 + Ralink RT3090 Wireless 802.11n 1T/1R
Software:
OS: Fedora 18, Kernel: 3.10.0-rc3+ (x86_64), Desktop: KDE 4.10.3, Display Server: X Server 1.13.3, Display Driver: nouveau 1.0.7, File-System: ext4, Screen Resolution: 1920x1080
Would you like to save these test results (Y/n): n
Timed Linux Kernel Compilation 3.1:
pts/build-linux-kernel-1.3.0
Test 1 of 1
Estimated Trial Run Count: 3
Estimated Time To Completion: 2 Minutes
Running Pre-Test Script @ 12:28:03
Started Run 1 @ 12:28:15
Running Interim Test Script @ 12:28:28
Started Run 2 @ 12:28:31
Running Interim Test Script @ 12:28:41
Started Run 3 @ 12:28:47
Running Interim Test Script @ 12:28:56 [Std. Dev: 5.03%]
Started Run 4 @ 12:29:00
Running Interim Test Script @ 12:29:09 [Std. Dev: 4.37%]
Started Run 5 @ 12:29:13
Running Interim Test Script @ 12:29:22 [Std. Dev: 3.79%]
Started Run 6 @ 12:29:26 [Std. Dev: 3.49%]
Running Post-Test Script @ 12:29:35
Test Results:
10.134061098099
9.3411478996277
9.2629590034485
9.3126730918884
9.4799311161041
9.3236708641052
Average: 9.48 Seconds
cor CPU %c0 GHz TSC SMI %c1 %c3 %c6 %c7 CTMP PTMP %pc2 %pc3 %pc6 %pc7 Pkg_W Cor_W GFX_W
38.61 3.59 3.39 0 9.64 3.04 48.71 0.00 43 43 0.00 0.00 0.00 0.00 26.30 20.35 0.00
0 0 34.73 3.67 3.39 0 13.33 3.02 48.93 0.00 43 43 0.00 0.00 0.00 0.00 26.30 20.35 0.00
0 4 41.86 3.52 3.39 0 6.19
1 1 33.48 3.66 3.39 0 12.53 4.00 49.99 0.00 40
1 5 40.62 3.52 3.39 0 5.39
2 2 34.41 3.66 3.39 0 18.06 2.98 44.55 0.00 35
2 6 48.26 3.58 3.39 0 4.22
3 3 35.79 3.69 3.39 0 10.70 2.16 51.36 0.00 40
3 7 39.77 3.50 3.39 0 6.71
--
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